1. Field of the Invention
The present invention relates to an X-ray mammography device of the type having an X-ray tube arrangement, a compression device, a subject table and a solid-state radiation detector. X-ray diagnostic means of this type serve to examine the breast of a patient.
2. Description of the Prior Art
X-ray mammography devices that are popular today operate with film-foil systems. These systems do not require a large space since the image sensor does not have to transmit electrical signals to the device.
The Siemens data sheet "MAMMOMAT 3000, OPDIMA--Digital biopsy and spot imaging system," (ref. no. WS 0597 7) teaches an X-ray mammography device in which a CCD image sensor is arranged in a cassette, this image sensor having a small image surface (49.times.85 mm.sup.2) compared to the cassette format (18.times.24 cm.sup.2). This CCD cassette is connected via a cable to a workstation which produces the mammographic X-ray images from the signals supplied by the CCD cassette. Since the CCD image sensor occupies only a small space in the cassette, the necessary electronics can be accommodated in this cassette as well without a problem. The rather small detector surface, however, is disadvantageous because it does not permit large-format examinations such as are known in film technology. If larger areas are to be examined, several exposures are necessary, which means a correspondingly increased radiation load on the examination subject. The cable also has a disruptive effect.
In newer X-ray mammography devices, solid-state image sensors such as a-Si panels are employed. Such panels, however, have relatively thick and in part bulky control and readout electronics arranged at the detector so that such detectors occupy a large volume. In order not to limit the variety of diagnostic methods of image capture, i.e. in order not to limit the acceptance of such devices, the detector surface area is reduced in order to keep the dimensions small.
There are also relatively thick sensor arrays with optical guides which complicate or prevent their application with adipose patients.
The dimensions of conventional solid-state detectors often exceed the length and width of the actual radiosensitive surface to a considerable degree. This is unacceptable for a solid-state mammography detector. Specific measures must therefore be taken which enable the active surface to be expanded to the edge of the cassette to within a millimeter.